From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 30988C7EE23 for ; Thu, 1 Jun 2023 02:16:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230359AbjFACQ0 (ORCPT ); Wed, 31 May 2023 22:16:26 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50760 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229672AbjFACQY (ORCPT ); Wed, 31 May 2023 22:16:24 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3FC4B121 for ; Wed, 31 May 2023 19:15:36 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1685585735; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=07+CNsneIoVDruoAxJKFo1HiC0RGLoxI/2tCL7nWfWk=; b=DPN8oA9bAO+JHMcfwTeNWMXD8E7sHSzOQeQKqq43gmf9Nmb2FWrc5mZgq+tYj6Ptc3EBx6 TwSMs0dRpf/Uzc6XHes13+6jEfYb2uAsZOWTHtq6fWTJxsADo4/F6JfxMEz1wQnjHxDnGr zKZ4WD//sKKWdrxLH0Rt+Zf4a7swyvk= Received: from mimecast-mx02.redhat.com (mx3-rdu2.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-455-0E5pcOXtMcCkmyYhinzlRw-1; Wed, 31 May 2023 22:15:29 -0400 X-MC-Unique: 0E5pcOXtMcCkmyYhinzlRw-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.rdu2.redhat.com [10.11.54.2]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id B24BD380450F; Thu, 1 Jun 2023 02:15:27 +0000 (UTC) Received: from localhost (ovpn-12-54.pek2.redhat.com [10.72.12.54]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 7829D40C6EC4; Thu, 1 Jun 2023 02:15:26 +0000 (UTC) Date: Thu, 1 Jun 2023 10:15:22 +0800 From: Baoquan He To: Anthony Yznaga Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, x86@kernel.org, hpa@zytor.com, dave.hansen@linux.intel.com, luto@kernel.org, peterz@infradead.org, rppt@kernel.org, akpm@linux-foundation.org, ebiederm@xmission.com, keescook@chromium.org, graf@amazon.com, jason.zeng@intel.com, lei.l.li@intel.com, steven.sistare@oracle.com, fam.zheng@bytedance.com, mgalaxy@akamai.com, kexec@lists.infradead.org Subject: Re: [RFC v3 00/21] Preserved-over-Kexec RAM Message-ID: References: <1682554137-13938-1-git-send-email-anthony.yznaga@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1682554137-13938-1-git-send-email-anthony.yznaga@oracle.com> X-Scanned-By: MIMEDefang 3.1 on 10.11.54.2 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 04/26/23 at 05:08pm, Anthony Yznaga wrote: > Sending out this RFC in part to guage community interest. > This patchset implements preserved-over-kexec memory storage or PKRAM as a > method for saving memory pages of the currently executing kernel so that > they may be restored after kexec into a new kernel. The patches are adapted > from an RFC patchset sent out in 2013 by Vladimir Davydov [1]. They > introduce the PKRAM kernel API. > > One use case for PKRAM is preserving guest memory and/or auxillary > supporting data (e.g. iommu data) across kexec to support reboot of the > host with minimal disruption to the guest. PKRAM provides a flexible way > for doing this without requiring that the amount of memory used by a fixed > size created a priori. Another use case is for databases to preserve their > block caches in shared memory across reboot. If so, I have confusions, who can help clarify: 1) Why kexec reboot was introduced, what do we expect kexec reboot to do? 2) If we need keep these data and those data, can we not reboot? They are definitely located there w/o any concern. 3) What if systems of AI, edge computing, HPC etc also want to carry kinds of data from userspace or kernel, system status, registers etc when kexec reboot is needed, while enligntened by this patch? Thanks Baoquan